[PATCH v3 5/5] arm/dom0less: introduce Kconfig for dom0less feature

[Luca Fancellu <luca.fancellu@xxxxxxx>]

Introduce a Kconfig for the dom0less feature, enabled by default,
to be able to choose if the feature should be compiled or not.

Provide static inline stubs when the option is disabled for the
functions externally visible.

Use the new Kconfig to remove dom0less DT binding from the efi-boot.h
code when the Kconfig is not enabled, do the same for
allocate_bank_memory inside domain_build.c that currently is used
only by dom0less-build.c module, but it's kept there provisioning
its usage by dom0 code.

Signed-off-by: Luca Fancellu <luca.fancellu@xxxxxxx>
---
Changes from v2:
 - protect allocate_bank_memory with the new Kconfig
---
 xen/arch/arm/Kconfig                      |  9 +++++++++
 xen/arch/arm/Makefile                     |  2 +-
 xen/arch/arm/domain_build.c               |  2 ++
 xen/arch/arm/efi/efi-boot.h               |  4 ++++
 xen/arch/arm/include/asm/dom0less-build.h | 12 ++++++++++++
 xen/arch/arm/include/asm/domain_build.h   |  2 ++
 6 files changed, 30 insertions(+), 1 deletion(-)

diff --git a/xen/arch/arm/Kconfig b/xen/arch/arm/Kconfig
index 0045a3762d86..0399f2faf734 100644
--- a/xen/arch/arm/Kconfig
+++ b/xen/arch/arm/Kconfig
@@ -88,6 +88,15 @@ config GICV2
          Driver for the ARM Generic Interrupt Controller v2.
          If unsure, say Y
 
+config DOM0LESS_BOOT
+       bool "Dom0less boot support" if EXPERT
+       depends on ARM
+       default y
+       help
+         Dom0less boot support enables Xen to create and start domU guests 
during
+         Xen boot without the need of a control domain (Dom0), which could be
+         present anyway.
+
 config GICV3
        bool "GICv3 driver"
        depends on !NEW_VGIC
diff --git a/xen/arch/arm/Makefile b/xen/arch/arm/Makefile
index 89ef0c9075b5..5daf8f10114d 100644
--- a/xen/arch/arm/Makefile
+++ b/xen/arch/arm/Makefile
@@ -15,7 +15,7 @@ obj-y += cpufeature.o
 obj-y += decode.o
 obj-y += device.o
 obj-$(CONFIG_IOREQ_SERVER) += dm.o
-obj-y += dom0less-build.init.o
+obj-$(CONFIG_DOM0LESS_BOOT) += dom0less-build.init.o
 obj-y += domain.o
 obj-y += domain_build.init.o
 obj-$(CONFIG_ARCH_MAP_DOMAIN_PAGE) += domain_page.o
diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c
index c2c17f075450..87eade449006 100644
--- a/xen/arch/arm/domain_build.c
+++ b/xen/arch/arm/domain_build.c
@@ -415,6 +415,7 @@ static void __init allocate_memory_11(struct domain *d,
     }
 }
 
+#ifdef CONFIG_DOM0LESS_BOOT
 bool __init allocate_bank_memory(struct domain *d, struct kernel_info *kinfo,
                                  gfn_t sgfn, paddr_t tot_size)
 {
@@ -476,6 +477,7 @@ bool __init allocate_bank_memory(struct domain *d, struct 
kernel_info *kinfo,
 
     return true;
 }
+#endif
 
 /*
  * When PCI passthrough is available we want to keep the
diff --git a/xen/arch/arm/efi/efi-boot.h b/xen/arch/arm/efi/efi-boot.h
index 1c3640bb65fd..689dc016d081 100644
--- a/xen/arch/arm/efi/efi-boot.h
+++ b/xen/arch/arm/efi/efi-boot.h
@@ -802,6 +802,7 @@ static int __init handle_module_node(const EFI_LOADED_IMAGE 
*loaded_image,
     return 1;
 }
 
+#ifdef CONFIG_DOM0LESS_BOOT
 /*
  * This function checks for boot modules under the domU guest domain node
  * in the DT.
@@ -849,6 +850,7 @@ static int __init handle_dom0less_domain_node(const 
EFI_LOADED_IMAGE *loaded_ima
 
     return mb_modules_found;
 }
+#endif
 
 /*
  * This function checks for xen domain nodes under the /chosen node for 
possible
@@ -876,6 +878,7 @@ static int __init efi_check_dt_boot(const EFI_LOADED_IMAGE 
*loaded_image)
     {
         int ret;
 
+#ifdef CONFIG_DOM0LESS_BOOT
         if ( !fdt_node_check_compatible(fdt_efi, node, "xen,domain") )
         {
             /* Found a node with compatible xen,domain; handle this node. */
@@ -884,6 +887,7 @@ static int __init efi_check_dt_boot(const EFI_LOADED_IMAGE 
*loaded_image)
                 return ERROR_DT_MODULE_DOMU;
         }
         else
+#endif
         {
             ret = handle_module_node(loaded_image, &dir_handle, node, addr_len,
                                      size_len, false);
diff --git a/xen/arch/arm/include/asm/dom0less-build.h 
b/xen/arch/arm/include/asm/dom0less-build.h
index d95cb6234b62..859944eece16 100644
--- a/xen/arch/arm/include/asm/dom0less-build.h
+++ b/xen/arch/arm/include/asm/dom0less-build.h
@@ -8,9 +8,21 @@
 #ifndef __ARM_DOM0LESS_BUILD_H_
 #define __ARM_DOM0LESS_BUILD_H_
 
+#ifdef CONFIG_DOM0LESS_BOOT
+
 void create_domUs(void);
 bool is_dom0less_mode(void);
 
+#else  /* !CONFIG_DOM0LESS_BOOT */
+
+static inline void create_domUs(void) {}
+static inline bool is_dom0less_mode(void)
+{
+    return false;
+}
+
+#endif /* CONFIG_DOM0LESS_BOOT */
+
 #endif  /* __ARM_DOM0LESS_BUILD_H_ */
 
 /*
diff --git a/xen/arch/arm/include/asm/domain_build.h 
b/xen/arch/arm/include/asm/domain_build.h
index 13118b5ff956..3950f0276e55 100644
--- a/xen/arch/arm/include/asm/domain_build.h
+++ b/xen/arch/arm/include/asm/domain_build.h
@@ -6,8 +6,10 @@
 
 typedef __be32 gic_interrupt_t[3];
 
+#ifdef CONFIG_DOM0LESS_BOOT
 bool allocate_bank_memory(struct domain *d, struct kernel_info *kinfo,
                           gfn_t sgfn, paddr_t tot_size);
+#endif
 int construct_domain(struct domain *d, struct kernel_info *kinfo);
 int domain_fdt_begin_node(void *fdt, const char *name, uint64_t unit);
 int make_resv_memory_node(const struct domain *d, void *fdt, int addrcells,
-- 
2.34.1